Investments - Realized Investment Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jun. 30, 2019
Gain (Loss) on Securities
Net investment gains (losses)		$ (11.0)	$ (2.3)	$ 153.3
Investment gain realized on transfer	$ 135.3
Reinsurance block of in-force fixed and variable annuity business		3,200.0		2,900.0	$ 2,900.0
Fixed maturity securities
Gain (Loss) on Securities
Net investment gains (losses)		(7.7)	9.4	141.4
Equity securities
Gain (Loss) on Securities
Net investment gains (losses)		(0.8)	1.8	16.0
Short-term and other investments
Gain (Loss) on Securities
Net investment gains (losses)		$ (2.5)	$ (13.5)	$ (4.1)